Rear area monitoring devices are used in automobiles and trucks in order to signal to the driver when reversing, e.g., when parking in a parking space, the distance of the rear of the vehicle from an obstruction or when the distance to the obstruction falls below a minimum distance. In relation to commercial vehicles, i.e., trucks and their trailers, rear area monitoring devices are used, e.g., to assist the driver in approaching a loading ramp in reverse. A rear area monitoring device is described in Applicant's DE 198 31 262 C2.